Psalms 58:4

Their poison is like the poison of a serpent: they are like the deaf adder that stoppeth her ear;

This psalm gives God's prophetic word about the punishment coming upon the wicked, not a personal expression of feeling against them. The word like means according to the likeness of, so the wicked are compared to a serpent by the likeness of their poison. Their poison is like a serpent's poison in that they carry deadly wickedness within that can break out and harm others, showing them harmful and unwilling to listen. They are like the deaf adder that stops its ear in deliberately and purposefully shutting the ear and refusing to listen to restraining counsel, warnings, and the charmer's voice. They refuse to hear warnings even when given clearly and wisely, rejecting God's warning of coming judgment and continuing in sin, worldliness, and rebellion while blind to danger as people were in Noah's day, and they will not believe until Christ's coming makes the judgment unmistakable.

The image calls sinners to awaken and listen to heaven's warnings delivered by prophets and saints and confirmed by the Spirit through signs and tokens, with the cross offered as their refuge, for those who reject Christ's instruction and wisdom reject what could restrain their evil and face a dreadful end. Shutting the ear also pictures covetous people who shut their ears to the cries of the poor and needy, gathering everything to themselves instead of sharing, and this selfishness keeps them from the fountain of everlasting love. The serpent-poison image shows slander as deadly, wounding like the sting of a deadly asp, targeting the innocent and bringing ruin. By contrast, the verse teaches wisdom in closing the ear to voices, enticements, and suggestions that would lead away from duty, right, and proper aim, while attending to God's voice. Listening to the tempter brings rebellion and sorrow as it did for the first parents, and ruin and death to humanity.